An offshore bank is a bank located outside the country of residence of the depositor. Typically, an individual or company will use an offshore bank in a low-tax jurisdiction (or tax haven) that provides financial and legal advantages. These advantages typically include:
easy access to deposits (at least in terms of regulation)
protection against local, political, or financial instability
While the term originates from the Channel Islands being "offshore" from the United Kingdom, and while most offshore banks are located in island nations to this day, the term is used figuratively to refer to any bank used for these advantages, regardless of location. Thus, an "offshore banks" include Swiss banks and those of other landlocked nations such as Luxembourg and Andorra.